Bone Cyst

Bone cysts are often asymptomatic and found incidentally on radiographs (see Tuberculosis Benign Bone Cyst, Radius, Ulnar). Sometimes, they may present with pain due to repeated hemorrhages or pathological fractures. Bone cysts include but are not limited to simple/unicameral bone cysts (SBC/UBC) and aneurysmal bone cysts (ABC). A simple bone cyst is a solitary, fluid-filled, benign bone cyst that may be unicameral (single chamber) or septated. It can involve any bone of extremities, the most common site being the proximal humerus and proximal femur (see Bone Cyst in Proximal Femur). In adults, the ilium and calcaneus are common locations. These lesions are most active during growth spurts and are known to heal spontaneously after bone maturity. Two-thirds of UBCs present with a fracture. UBCs in flat bones are often asymptomatic unless detected incidentally on imaging. An aneurysmal bone cyst is a rare, locally destructive, blood-filled, benign cystic bone tumor. It involves the metaphysis of long bones in children and young adults. They can involve any bone, but the most common sites are the distal femur, proximal tibia, proximal humerus, and spine. Most cases present with mild to moderate pain. The rapid growth of lesions may mimic malignancy. Spinal lesions may cause radicular pain or neurologic deficits. They often involve posterior elements of the vertebral bodies. Exceptionally, ABC can also arise in soft tissue. See Ankle Radiograph, Aneurysmal Bone Cyst (ABC).